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<div class="sect1">
<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="xmlsec-notes-encrypt"></a>Encrypting data.</h2></div></div></div>
<p>The typical encryption process includes following steps:
	  </p>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem"><p>
		Prepare data for encryption.
	    </p></li>
<li class="listitem"><p>
		Create or load encryption template and select start
		&lt;enc:EncryptedData/&gt; node.
	    </p></li>
<li class="listitem"><p>
		Create encryption context <a class="link" href="xmlsec-xmlenc.html#xmlSecEncCtx" title="struct xmlSecEncCtx">xmlSecEncCtx</a>
		using <a class="link" href="xmlsec-xmlenc.html#xmlSecEncCtxCreate" title="xmlSecEncCtxCreate ()">xmlSecEncCtxCreate</a> or
		<a class="link" href="xmlsec-xmlenc.html#xmlSecEncCtxInitialize" title="xmlSecEncCtxInitialize ()">xmlSecEncCtxInitialize</a>
		functions.
	    </p></li>
<li class="listitem"><p>
		Load encryption key in <a class="link" href="xmlsec-keysmngr.html#xmlSecKeysMngr" title="struct xmlSecKeysMngr">keys manager</a> 
		or generate a session key and set it in the encryption context
		(<em class="structfield"><code>encKey</code></em> member of 
		<a class="link" href="xmlsec-xmlenc.html#xmlSecEncCtx" title="struct xmlSecEncCtx">xmlSecEncCtx</a> structure).
	    </p></li>
<li class="listitem">
<p>
		Encrypt data by calling one of the following functions:
		</p>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: circle; ">
<li class="listitem"><p>
			<a class="link" href="xmlsec-xmlenc.html#xmlSecEncCtxBinaryEncrypt" title="xmlSecEncCtxBinaryEncrypt ()">xmlSecEncCtxBinaryEncrypt</a>
		    </p></li>
<li class="listitem"><p>
			<a class="link" href="xmlsec-xmlenc.html#xmlSecEncCtxXmlEncrypt" title="xmlSecEncCtxXmlEncrypt ()">xmlSecEncCtxXmlEncrypt</a>
		    </p></li>
<li class="listitem"><p>
			<a class="link" href="xmlsec-xmlenc.html#xmlSecEncCtxUriEncrypt" title="xmlSecEncCtxUriEncrypt ()">xmlSecEncCtxUriEncrypt</a>
		    </p></li>
</ul></div>
<p>
	    </p>
</li>
<li class="listitem"><p>
		Check returned value and if necessary consume encrypted data.
	    </p></li>
<li class="listitem"><p>
		Destroy encryption context <a class="link" href="xmlsec-xmlenc.html#xmlSecEncCtx" title="struct xmlSecEncCtx">xmlSecEncCtx</a>
		using <a class="link" href="xmlsec-xmlenc.html#xmlSecEncCtxDestroy" title="xmlSecEncCtxDestroy ()">xmlSecEncCtxDestroy</a> or
		<a class="link" href="xmlsec-xmlenc.html#xmlSecEncCtxFinalize" title="xmlSecEncCtxFinalize ()">xmlSecEncCtxFinalize</a>
		functions.
	    </p></li>
</ul></div>
<p>
	</p>
<p>
	     </p>
<div class="example">
<a name="id-1.2.6.4.3.1"></a><p class="title"><b>Example 11. Encrypting binary data with a template.</b></p>
<div class="example-contents">
<pre class="programlisting">
/**
 * encrypt_file:
 * @tmpl_file:		the encryption template file name.
 * @key_file:		the Triple DES key file.
 * @data:		the binary data to encrypt.
 * @dataSize:		the binary data size.
 *
 * Encrypts binary #data using template from #tmpl_file and DES key from
 * #key_file.
 *
 * Returns 0 on success or a negative value if an error occurs.
 */
int 
encrypt_file(const char* tmpl_file, const char* key_file, const unsigned char* data, size_t dataSize) {
    xmlDocPtr doc = NULL;
    xmlNodePtr node = NULL;
    xmlSecEncCtxPtr encCtx = NULL;
    int res = -1;
    
    assert(tmpl_file);
    assert(key_file);
    assert(data);

    /* load template */
    doc = xmlParseFile(tmpl_file);
    if ((doc == NULL) || (xmlDocGetRootElement(doc) == NULL)){
	fprintf(stderr, "Error: unable to parse file \"%s\"\n", tmpl_file);
	goto done;	
    }
    
    /* find start node */
    node = xmlSecFindNode(xmlDocGetRootElement(doc), xmlSecNodeEncryptedData, xmlSecEncNs);
    if(node == NULL) {
	fprintf(stderr, "Error: start node not found in \"%s\"\n", tmpl_file);
	goto done;	
    }

    /* create encryption context, we don't need keys manager in this example */
    encCtx = xmlSecEncCtxCreate(NULL);
    if(encCtx == NULL) {
        fprintf(stderr,"Error: failed to create encryption context\n");
	goto done;
    }

    /* load DES key */
    encCtx-&gt;encKey = xmlSecKeyReadBinaryFile(xmlSecKeyDataDesId, key_file);
    if(encCtx-&gt;encKey == NULL) {
        fprintf(stderr,"Error: failed to load des key from binary file \"%s\"\n", key_file);
	goto done;
    }

    /* set key name to the file name, this is just an example! */
    if(xmlSecKeySetName(encCtx-&gt;encKey, key_file) &lt; 0) {
    	fprintf(stderr,"Error: failed to set key name for key from \"%s\"\n", key_file);
	goto done;
    }

    /* encrypt the data */
    if(xmlSecEncCtxBinaryEncrypt(encCtx, node, data, dataSize) &lt; 0) {
        fprintf(stderr,"Error: encryption failed\n");
    	goto done;
    }
        
    /* print encrypted data with document to stdout */
    xmlDocDump(stdout, doc);
    
    /* success */
    res = 0;

done:    
    /* cleanup */
    if(encCtx != NULL) {
	xmlSecEncCtxDestroy(encCtx);
    }
    
    if(doc != NULL) {
	xmlFreeDoc(doc); 
    }
    return(res);
}
		</pre>
<p><a class="link" href="xmlsec-encrypt-template-file.html#xmlsec-example-encrypt1" title="encrypt1.c">Full program listing</a></p>
<p><a class="link" href="xmlsec-encrypt-template-file.html#xmlsec-example-encrypt1-tmpl" title="encrypt1-tmpl.xml">Simple encryption template file</a></p>
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